500 series Level-Loc project

[JAY X]

Ah!, ok then!, because i will use a TO92 9v regulator to power it, and it supplies a max of 100ma.

Thanks a lot!

Jay x

 

[Whoops]

Probably it’s fine, but I’m not sure what’s the current draw

 

[JAY X]

Hi!

I have a question, In this build, the 50k log gain pot gnd is connected directly to gnd, but in other builds, the gnd of the pot is connected to gnd through a resistor of 2k2 or 3k. ¿why?

 

[grid_stopper]

Ive got a couple questions, if someone smarter than me cares to chime in:

working of the schematic on page 1:

-if I wanted to add a simple hpf to the side-chain input, would that be as simple as changing the value of C11? am i way off?

-If i am intending to occasionally bypass the compressor and use the amplifier only, would disconnecting that same C11 via a switch do that in an acceptable way?

-what would be the most efficient way to add an LED that shows when gain reduction is occurring?

 

[dmp]

-if I wanted to add a simple hpf to the side-chain input, would that be as simple as adding a cap in parallel with C11? am i way off?

I think the input to the sidechain is C10. (C11 is heading toward UB-RET, which is the wet signal). I would look at reducing C10 to HPF the sidechain input. C10 and R28 form a HPF with the corner freq at 1/(2*PI*RC). Best way to do this is find the size cap you need for the HPF 'on' and install it for C10, then add a large cap in parallel with a switch to turn the HPF 'off'.

-If i am intending to occasionally bypass the compressor and use the amplifier only, would disconnecting that same C11 via a switch do that in an acceptable way?

Look at how the 1176 does this, with the switch on the attack pot. The input to the sidechain, capacitor C10, is grounded. You would not want to ground the junction (i.e. C9 R19) just disconnect C10 from that junction and connect to ground with a SPDT.

-what would be the most efficient way to add an LED that shows when gain reduction is occurring?

You could add a GR meter the way the 1176 does by having a second FET, matching Q1, that drives a meter circuit.

 

[grid_stopper]

I think the input to the sidechain is C10. (C11 is heading toward UB-RET, which is the wet signal). I would look at reducing C10 to HPF the sidechain input. C10 and R28 form a HPF with the corner freq at 1/(2*PI*RC). Best way to do this is find the size cap you need for the HPF 'on' and install it for C10, then add a large cap in parallel with a switch to turn the HPF 'off'.

I just realized i was working off the older sherlock schematic, and not the one in this thread, looking at the sherlock scheme and its C11 is the C10 in this 500 series version, so it seems im on the right track, excellent.

Look at how the 1176 does this, with the switch on the attack pot. The input to the sidechain, capacitor C10, is grounded. You would not want to ground the junction (i.e. C9 R19) just disconnect C10 from that junction and connect to ground with a SPDT.

this makes sense, thank you.

You could add a GR meter the way the 1176 does by having a second FET, matching Q1, that drives a meter circuit.

this could work nicely, assuming it isnt overly complex to get the FET to drive the LED

 

[dmp]

If you just want a LED to turn on when the unit is compressing, use the sidechain voltage to trigger a LED above a certain threshold. Do a search for "comparator LED circuit".

 

[grid_stopper]

If you just want a LED to turn on when the unit is compressing, use the sidechain voltage to trigger a LED above a certain threshold. Do a search for "comparator LED circuit".

now we're cookin, ill look into this- thank you!

 

[grid_stopper]

OK, this simple circuit from Rod Elliot seems like a good candidate to do what i need but i have another stupid question- will this require a separate FET like in the 1176, or can i get by with only the one?

 

[mihi_fuchs]

Is the INA134 correct here? It is 0 dB, whereas the INA137 is -6 dB. The drv134 is +6dB, so as a pair, the ina137 / drv134 would be unity.
Maybe either works and it doesn't matter?

I used THAT ics instead. 1240 and 1646. both 0db - works perfectly.

 

[mihi_fuchs]

Here's a current build:



all data can be found here:
https://www.dropbox.com/scl/fo/0uxyml0loh16wyv5arf9p/h?rlkey=z4yy28f3glmo9ecob1ixs4fny&dl=0

There are also sound samples on a drum bus for those interested.

Cheers
Michael

 

[materials to outlet]

Hi Michael,
do you have a part number or description for the screwhole parts that slot into the PCB for screwing on the face plate?
Also, what is the length of the standoffs that go between the two boards?
Thanks!

 

[mihi_fuchs]

Hi,

PCB standoffs are 25 mm; the mounting holes work with M4 or M3 screws. Sorry, I do not have the US units at hand - but sure it's easy to find out.
the PCB-frontpanel connectors are Richco SEI-2. https://www.buerklin.com/en/p/richc...r_name=Richco&sort=8399_material,asc#download
Let me know if those are easily available in the US. Otherwise I should have still a few left.

Best regards,
Michael

 

[mihi_fuchs]

Hi,

PCB standoffs are 25 mm; the mounting holes work with M4 or M3 screws. Sorry, I do not have the US units at hand - but sure it's easy to find out.
the PCB-frontpanel connectors are Richco SEI-2. https://www.buerklin.com/en/p/richc...r_name=Richco&sort=8399_material,asc#download
Let me know if those are easily available in the US. Otherwise I should have still a few left.

Best regards,
Michael

BOM in the dropbox folder got updated accordingly - please use the updated BOM. You can find these parts below the mouser list as "additional".

Parts added/corrections:
connectors
screws
standoffs
heatsink
Q8,9 were missing and have been added
# of 2n5089 has been corrected (must be 6 pieces)

 

[mihi_fuchs]

Hi,

PCB standoffs are 25 mm; the mounting holes work with M4 or M3 screws. Sorry, I do not have the US units at hand - but sure it's easy to find out.
the PCB-frontpanel connectors are Richco SEI-2. https://www.buerklin.com/en/p/richc...r_name=Richco&sort=8399_material,asc#download
Let me know if those are easily available in the US. Otherwise I should have still a few left.

Best regards,
Michael

you can also use the SEI-3 with M3 screws as far as I can see. Dimensions should be the same.
https://www.buerklin.com/en/p/richco/pcb-fasteners/sei-3/17H946/

Best regards,
Michael

 

[mihi_fuchs]

Here's a current build:

View attachment 127911View attachment 127912
View attachment 127914View attachment 127916View attachment 127915View attachment 127917View attachment 127918
all data can be found here:
https://www.dropbox.com/scl/fo/0uxyml0loh16wyv5arf9p/h?rlkey=z4yy28f3glmo9ecob1ixs4fny&dl=0

There are also sound samples on a drum bus for those interested.

Cheers
Michael

Here is the new frontpanel for my version of the built. It's CNC machined and the labeling is silk screened. I got 15 panels leftover. You can find those on the black market:


https://groupdiy.com/threads/frontpanels-for-fum-lvl-lok-compressor-in-500-format.88677/

Best regards,
Michael

 

[HerbertR]

I've finally found the time to finish a pair of Lev Locs. Very, very evil toys. From strong pumping to light, warm scratching to fat distortion. Compared to the Devil Loc plugin, the hardware offers significantly more options for sound variations and a much more "organic" character if you control the input level correctly. I connected the front panel to ground directly with a cable to avoid hum induction when touching the front panels during tests. However, this should no longer be necessary after installation in the 500 rack. Many thanks to Michi and Irfrench for this professional, great project... awesome....

 

[Jim50hertz]

@HerbertR what value did you use for r25? 2k2?

 

[HerbertR]

@HerbertR what value did you use for r25? 2k2?

Hi, I also went with 22K on R25.

 

[Jim50hertz]

Interesting! I’ll socket r25 and try both. Thanks @HerbertR